公路改扩建高边坡既有锚杆受力特性离心试验

Centrifugal Test on Stress Characteristics of Existing Bolts in High Slope of Highway Reconstruction and Expansion

为研究改扩建边坡二次开挖下既有锚杆的受力特性及边坡稳定性,基于自主研发的模型试验锚杆角度支护装置,采用离心试验研究了锚固角度分别为10°、20°、30°、45°、60°及锚杆横向密度分别为1根/(18 cm)、1根/(12 cm)下顺层岩质高边坡开挖全过程中坡顶水平位移、锚杆轴力及坡内土压力变化规律。结果表明:相同锚固角度下,随着边坡开挖卸荷,坡顶累计水平位移非线性增加,且开挖坡顶增幅较开挖坡中大;锚杆轴力呈单峰分布,在开挖坡顶及坡脚时轴力增幅较大,轴力峰值靠近软弱面且随开挖卸荷先减小后增大,开挖后轴力峰值仍为开挖前的61%以上;随锚固角度的增加,坡顶水平位移先减小后增大,坡内土压力先增大后减小,即存在最佳锚固角度;建议边坡开挖宜采用分级开挖,并在开挖坡顶及坡脚时适当降低速率,综合考虑边坡坡度、岩层及软弱面倾角等因素,合理设计锚固角度。研究成果有助于工程技术人员在改扩建边坡二次开挖工程中选择合适的支护措施。

To investigate the stress characteristics of existing bolts and slope stability during secondary excavation in a slope reconstruction and expansion project,we conducted centrifugal test by using self-developed bolt angle support device for model test.The horizontal displacement at the slope’s crest,bolt axial force,and soil pressure throughout the excavation process on a bedding rock slope were examined.The anchoring angles studied were 10°,20°,30°,45°,and 60°,with one bolt per 18 cm and per 12 cm,respectively.Results indicate that under the same anchoring angle,cumulative horizontal displacement at the crest increases nonlinearly with slope unloading,notably exceeding that at the mid-slope.The axial force of bolt exhibits a unimodal distribution,peaking during excavations at slope crest and toe.Peak axial force,near the weak surface,initially declines and then rises with excavation unloading,remaining over 61%of pre-excavation levels.As anchoring angle increases,slope crest displacement initially decreases then rises,while soil pressure follows an inverse trend,suggesting an optimal anchoring angle.We recommend staged slope excavation,with reduced excavation rates at the crest and toe.Slope gradient,rock strata,and weak surface inclination should be considered in anchoring angle design for optimal performance.The research findings are conducive to selecting appropriate support measures in secondary excavation of slopes.